Backflow preventer valve

ABSTRACT

An insertable backflow preventer is presented. The backflow preventer is provided with a cylindrical housing. The housing has a flow transition zone, a proximal orifice/ball seat, a ball with a specific weight that equals or is close to the specific weight of the surrounding fluid, and a distal retaining screen. The housing can have a flange provided on the outside of the housing at one end to facilitate securing the valve in a pipe. The valve is self-cleaning, can be placed in any orientation in a pipe and has low hydraulic head-loss. The valve&#39;s unique cost-effective design provides for easy and relative quick installation, eliminates the need to reconfigure existing plumbing, and can be performance tested remotely. Properly installed, it can dramatically improve the security of, for example, potable water sources in a building or other context, and inasmuch as when installed it is not visible, it is tamper proof. The valve can be scaled to any size pipe or tube, and due to its internal flow dynamics is self cleaning. Multiple valves can be installed in series, and balls of varying specific weight can be used in each valve in such a series to allow for contexts where a range of fluids are sent through the same line, or to provide fail-safe operation in the event that contaminants change the specific gravity of the fluid.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. Nos. 60/811,676, filed on Jun. 6, 2006; 60/847,242,filed on Sep. 26, 2006; and 60/905,386, filed on Mar. 6, 2007.

TECHNICAL FIELD

The present invention relates to water delivery systems, and inparticular to a backflow preventer valve for use to increase thesecurity of, and prevent tampering with, water supplies.

BACKGROUND OF THE INVENTION

Backflow preventers are used to prevent contamination of a buildingand/or public water distribution system by reducing or eliminatingbackflow of a contaminated hazardous fluid into the respectivesystem(s). Conventional backflow preventers are mechanicallysophisticated devices, that are threaded for pipes, unthreaded fortubing, or flanged at each end so they can be installed, i.e., splicedinto the piping system. Conventional backflow preventers requireperiodic inspection, testing, maintenance and repair. Therefore, theymust be visible and accessible. As such they are not tamper resistant ortamperproof. A conventional backflow preventer is usually, but notalways, installed in a pipeline between a main municipal water supplyline and a service line that feeds an installation, e.g., hospital,industrial building, commercial establishments, multiple or singlefamily residences. A conventional backflow prevention valve is anassembly that typically includes two check valves that are configured topermit fluid flow in one direction, such as from a main municipal watersupply distribution pipe system to a particular building's service(pipe) line. They are generally costly to purchase and, always laborintensive to install. Conventional backflow preventers are commonly usedin buildings equipped with chemical processing equipment, sprinklersystems, etc. Backflow preventers are required by applicable plumbingcodes to protect a building's potable water supply from accidentalcontamination, a condition that would occur from a cross connection andflow reversal in a branch or pipe riser, due to a process or systemmalfunction. Left unchecked, hydraulic reversal can compromise thequality and safety of a building's potable water supply system and,potentially, the municipal water supply distribution system as well.Nonetheless, current plumbing design and operating codes are essentiallysilent regarding protective measures against the willful intent of anindividual (such as, for example, a terrorist, criminal, etc.) to injecta toxic contaminant into a building's potable water supply plumbingsystem and possibly the municipal water supply system, including firehydrants, as well.

Historically, a typical backflow preventer consisted of a mechanicalsingle spring-loaded check valve in a water supply line, generallyplaced between a pair of gate-type shutoff valves. Current buildingcodes, however, now require backflow preventers to include a pair ofindependently spring-loaded positive check valves. The motivation behindsuch a rule is that should one of the check valves fail, the secondvalve can serve as a backup. Because of their mechanical complexity,current plumbing codes typically require that the check valve(s) bereplaceable and repairable while on-line, that is, without shutting downthe system. In contrast, current plumbing codes for commercial,industrial, multi-story residential buildings and single homes do notrequire the installation of backflow preventers. This leaves suchbuildings' internal potable drinking water supply vulnerable tocompromise via injection of a toxic chemical or biological contaminantinto the building's water supply system, with the added possibility ofcontaminating the municipal water supply distribution system in theprocess. The latter could compromise the water quality of an entireregional water distribution grid. In light of the health and safetyconcerns previously described, it is imperative that appropriatemeasures be immediately initiated to address and bridge this criticalgap in security as it relates to existing and future potable drinkingwater systems.

While municipal codes generally require the replacement of single checkvalves with a double check valve backflow preventer, simply requiringbuilding owners to undertake major re-plumbing to install these backflowpreventers between the municipal water service distribution lineslocated in the street and downstream of the building's water meter wouldnot address the vulnerability to intentional internal contaminationwithin a given building. Retrofitting a conventional backflow preventerto protect a building's internal potable water distribution system frompossible intentional contamination at every point-of-use water supplyterminus, such as, for example, via shutoff valves for kitchen andbathroom fixtures, drinking water fountains, etc., could be veryexpensive. Each existing supply line would have to be re-plumbed toprovide space to accommodate a single conventional check valve assembly.Moreover, access for repair and replacement must be provided for eachsuch back flow preventer to provide for proper maintenance, since thesedevices are generally internally mechanically complex. Even in newconstruction, installation of conventional back flow preventers for eachpoint-of-use fixture would be costly.

As noted in a Jun. 18, 2004 article entitled “Cross Connection ControlPrograms And Backflow Preventers Are Essential Components of SafeDrinking Water Systems,” published on Backflow Prevention TechZone (atrade web site at URL http://www.backflowpreventiontechzone followed by.com), plumbing system cross connections between potable and non-potablewater supplies, water using equipment, and drainage systems, continue tobe a serious potential public health hazard worldwide. Anywhere peoplecongregate and utilize communal water supplies, water using equipment,and drainage systems, the danger of un-protected cross connectionscontinue to threaten public health. Thus, there is a wideningrecognition that properly installed, maintained, and tested backflowprevention devices are critical elements of safe drinking water systemsin our communities and workplaces. The report further noted thatbackflow preventer device development, beyond simple check valves, beganto accelerate and diversify in the mid-20th century, but potable(“city”) water piping systems and water using equipment, especiallyinside industrial and medical buildings, have grown exponentially incomplexity and are also continuously altered. Surveys over the decadeshave shown that water using devices and equipment which can contaminatea drinking water system continue to be connected to potable waterlineswithout properly selected, permitted, installed, maintained, and ifappropriate for the device, tested and certified, backflow preventervalves. Thus, “despite decades of new public health and occupationalsafety laws, as well as updated and revised plumbing codes, along withnew improved backflow preventer devices, the cross connection problemcontinues to be an ongoing dynamic one.”

The most universal backflow hazards are constantly re-created, such asin cross-connections within residential and public washrooms, andordinary, unprotected from backflow, hose connections. The bathroomcontinues to be a repository of one of the subtle yet potentiallydramatic backflow hazards found recurrently in homes and public places.Many local health departments have “blue water” flowing from the kitchensink reports in their archives, which may well be only the tip of theiceberg of un-documented incidents of actual backflow from an unapprovedor improperly installed toilet fill-valve assembly.

As further noted in the report cited above, recent cross connectioninspection surveys (USC/FCCCHR) continue to reveal that the mostprevalent and potentially hazardous potable water plumbing crossconnection is the common hose connection (or hose bib) (UF/IFAS, 3/95)found in virtually every home and building. The predominant cause forthe cross connection, known as backsiphonage, is the sudden andsignificant loss of hydraulic pressure in the water main. Excessivedrops in water pressure, have historically, been attributed to a brokenwater main, a fire nearby where the Fire Department is using largequantities of water, or by a water company official opening a firehydrant to test it. Buildings near a municipal water main break or afire hydrant being opened will experience a lowering of the waterpressure and possibly backsiphonage.

Conventionally, potable water backflow protection has been addressed byvarious valve types, having unique design configurations. Such designsinclude, for example, Air Gap, Atmospheric Vacuum Breaker, PressureVacuum Breaker, Double Check Valve, and Pressure Reducer. Such devicesare external in their intended application, limited to a specificinstallation orientation, e.g., vertical or horizontal, visible, must beeasily accessible and are thus vulnerable to tampering, are mechanicallycomplex to the extent that periodic inspections and maintenance arerequired and without proper servicing are unreliable in the long term,and are operationally affected by gravity in whole or part.

For example, the air gap backflow preventer, considered by some to bethe “ultimate” backflow preventer, is totally reliant on gravity tooperate properly, and must be installed in an external manner. Inaddition, all conventional backflow preventers, because of theirinherent design, are prone to clogging and fouling. Four of the fiveaforementioned must utilize a plurality of individual valve means andsprings to prevent backflow. Such mechanical complexity actually fosterscorrosion, clogging and/or fouling, and thus are unsuitable to resolvein a cost-effective manner the aforementioned public drinking watersupply safety concerns. Additionally, conventional backflow valvesrequire a great deal of effort in both labor and material to beinstalled, and as a result of their design must always be readilyaccessible, i.e., exposed, to provide for required periodic maintenance.Such valves thus offer a perfect access point for a terrorist.

A recent GAO-04-29 report to the United States Senate Committee onEnvironment specifically referenced fire hydrants as a topvulnerability. Moreover, as recently reported by the American WaterWorks Association on May 2, 2007, terror training manuals found inAfghanistan showed plans to contaminate America's water supply.

Thus, there is a compelling need for a backflow preventer device that issimple in its design and operation, not visible from publicly accessibleareas, tamper-resistant, easy to install in any plumbing pipingconfiguration, essentially maintenance free, and truly cost-effective tomanufacture, install and operate.

SUMMARY OF THE INVENTION

An insertable backflow preventer is presented. The backflow preventer isprovided with a cylindrical housing, and can be easily inserted into anystandard size NPS pipe or copper tube. The apparatus can also have anexternal flange at one end to secure its position when inserted into theexposed end of a pipe or tube, as the flange insures that the checkvalve can never be inserted backwards. The housing can have a flowtransition zone, a proximal orifice/ball seat, a ball with a specificweight that is a function of that of the surrounding fluid, and a distalretaining screen. The housing can have a flange provided on the outsideof the housing at one end to facilitate securing the valve in a pipe.The valve can be self-cleaning, can be placed in any orientation in apipe and has low hydraulic head-loss. The valve's unique cost-effectivedesign provides for easy and relative quick installation, eliminates theneed to reconfigure existing plumbing, and can be performance testedremotely. Properly installed, it can dramatically improve the securityof, for example, potable water sources in a building or other context,and inasmuch as when installed it is not visible, it is tamper proof.The valve can be scaled to any size pipe or tube. Multiple valves can beinstalled in series, and balls of varying specific weights can be usedin each valve in such series to allow for contexts where a range offluids are sent through the same line, or to provide fail-safe operationin the event that contaminants change the specific gravity of the fluid.The housing can have a fluid inlet, a main flow conduit and a fluidoutlet. The caged ball can move freely within the internal space betweenthe distal retaining screen and the proximal orifice/seat, essentiallylongitudinally. The movement and position of the ball within the valveis governed by the direction and rate of flow of the fluid surroundingthe ball. In exemplary embodiments of the present invention the ball andinternal structures of the entire apparatus can be made smooth so as tominimize fluid head-loss, insure that the caged suspended ball can movefreely therein, seat correctly in the valve orifice/seat, and instantlyrespond to changes in fluid pressure, whether large or small, anddirection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-sectional view of an exemplary insertablebackflow preventer under a normal flow (forward flow) conditionaccording to an exemplary embodiment of the present invention;

FIG. 2 illustrates an exemplary cross-sectional view of an exemplaryinsertable backflow preventer under a backflow (reverse flow) conditionaccording to an exemplary embodiment of the present invention;

FIG. 3 illustrates an end view of an exemplary retaining screenaccording to an exemplary embodiment of the present invention;

FIG. 4 depicts an exemplary operational illustration of an insertablebackflow preventer according to an exemplary embodiment of the presentinvention;

FIG. 5 is a longitudinal cross sectional perspective view of anexemplary backflow preventer installed in a pipe according to anexemplary embodiment of the present invention;

FIGS. 6( a)-(c) depict exemplary force diagrams for an exemplarybackflow preventer insert valve according to an exemplary embodiment ofthe present invention;

FIG. 7 is a graph of flow rate versus head loss for an exemplarybackflow preventer valve according to an exemplary embodiment of thepresent invention;

FIG. 8 illustrates an exemplary BFP installation for a sink according toan exemplary embodiment of the present invention;

FIG. 9 illustrates an exemplary BFP installation upstream of a shutoffvalve on the utility's side of a water meter according to an exemplaryembodiment of the present invention;

FIG. 10 illustrates an exemplary BFP installation for a toilet accordingto an exemplary embodiment of the present invention;

FIG. 11 illustrates an exemplary BFP installation in copper tubingaccording to an exemplary embodiment of the present invention;

FIG. 12 illustrates depicts a conventional shutoff valve connected to aconventional flapper check valve;

FIG. 13 shows the setup of FIG. 12 with a BFP according to an exemplaryembodiment of the present invention;

FIG. 14 depicts the setup of FIG. 13 with the BFP partially exposed;

FIG. 15 depicts the setup of FIGS. 13 and 14 as it would appear afterinstallation;

FIG. 16 depicts a rear-end view of a BFP according to an exemplaryembodiment of the present invention;

FIG. 17 depicts a close front-end view of a seated check ball of anexemplary BFP according to an exemplary embodiment of the presentinvention;

FIG. 18 depicts the view of FIG. 17 without the check ball;

FIG. 19 depicts the retaining screen of FIGS. 17 and 18 and the ballcage of an exemplary BFP according to an exemplary embodiment accordingto the present invention;

FIG. 20 depicts the check ball orifice and seat of an exemplary BFPaccording to an exemplary embodiment of the present invention;

FIG. 21 depicts the orifice and seat of FIG. 20 with a check ballproperly seated therein;

FIG. 22 depicts a rear-end view (similar to that of FIG. 16) of anexemplary BFP with a check ball seated in its orifice as shown in FIG.21;

FIG. 23 depicts the front-end view of FIG. 19 with a check ball seatedon the retaining screen (forward flow);

FIG. 24 depicts a side-view of a BFP and gasket according to anexemplary embodiment of the present invention;

FIG. 25 is an expanded view of the BFP shown in FIG. 24;

FIG. 26 depicts dual BFP insert valves in an exemplary fire hydrantretrofit according to an exemplary embodiment of the present invention;

FIG. 27 is a top view of the exemplary retrofitted fire hydrant of FIG.26;

FIG. 28 depicts a expanded side view of an exemplary dual BFP firehydrant retrofit according to an exemplary embodiment of the presentinvention;

FIG. 29 is a detailed top view of the retrofit assembly depicted in FIG.27;

FIG. 30 is a front view of the exemplary hydrant retrofit assembly ofFIG. 29;

FIG. 31 is a side view of the exemplary hydrant retrofit assembly ofFIGS. 29 and 30;

FIG. 32 illustrates an exemplary conventional fire hydrant;

FIG. 33 depicts the exemplary fire hydrant of FIG. 32 with dual BFPinternal inserts according to an exemplary embodiment of the presentinvention;

FIG. 34 depicts an exemplary new fire hydrant with dual BFP inserts in alateral pipe according to an exemplary embodiment of the presentinvention; and

FIG. 35 depicts an exemplary new fire hydrant with a single BFP insertin a lateral pipe according to an exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described with reference to variousexemplary embodiments. It should be understood that none of suchdescriptions are limiting, and all descriptions of exemplary embodimentsand their respective components are exemplary, and for illustrativepurposes. The present invention is understood to be capable ofimplementation in various other embodiments and variations ofembodiments than those described herein, as will be understood by thoseskilled in the art.

In exemplary embodiments of the present invention, an insertablebackflow preventer valve (hereinafter sometimes referred to as a “BFP”)can have a ball, and a valve housing. The housing can be provided in twoparts which can, for example, be screwed together to hold the balltherebetween. The housing can have, for example, a retaining screen onits front end (the distal, or outflow side) and a sealable orifice atits rear end (the proximal, or inflow side). The retaining screen can beprovided so as to provide for normal flow through it with minimal headloss, and the sealable orifice can be provided such that the ballclosably seals with it in a backflow condition. The valve housing canhave a flow transition zone so as to obviate forward flow head pressureloss. In normal operation (forward flow) the ball seats in a hub at thecenter of the retaining screen, and rotates in a random manner on a thinlayer of fluid between it and said hub, providing for a self cleaningaction. Various aspects of exemplary BFPs according to exemplaryembodiments of the present invention are next described.

FIG. 1 illustrates a cross-sectional view of an exemplary insertablebackflow preventer according to an exemplary embodiment of the presentinvention. Visible are a thin walled cylindrical housing 30 having anoutside diameter that is slightly smaller than the internal diameter ofpipe 20, thus providing means for the unobstructed insertion of saidinsertable backflow preventer assembly into the exposed end (left sideof figure) of pipe 20. The assembly can be positioned in anyorientation, i.e., horizontal or vertical, when a given plumbing supplysystem's shutoff valve (not shown) is removed.

While FIGS. 1-11 are schematics, FIGS. 16-25 depict an actual exemplaryBFP prototype according to an exemplary embodiment of the presentinvention. Thus, FIGS. 16-25 will be referred to illustrate variousaspects of the description of FIGS. 1-4, using the same index numbers asshown in FIGS. 1-3 for convenience, index numbers not being reproducedon FIGS. 16-25 for ease of viewing.

Thus, FIG. 24 depicts a side view of an exemplary fully assembled BFP,and FIG. 25 illustrates such a BFP in an expanded view, showing the twoportions of the housing 30 and the check ball 5, as well as a washer onthe proximal side of a distal flange. These views accurately show themechanical and physical simplicity of the BFP, a springless caged ballcheck valve that be easily inserted into a pipe or copper tube andhaving only one moving element.

FIGS. 13 and 14 depict an exemplary BFP, similar to that of FIGS. 24 and25, being installed on the supply side of such a shut-off valve. The BFPcan be installed, as shown, by opening the connection between theshut-off valve and the supply line. FIG. 15 depicts the same BFP asfully installed, and thus invisible from the outside.

Returning to FIG. 1, on the distal end of the BFP can be seen flange 50and washer 10, which can, for example, easily fix, seal and position theBFP within pipe 20 and a shutoff valve, where the thickness of flange 50is sufficiently small so as to allow a complete connection between thepipe and the upstream end fitting of the shutoff valve or otherconnection, as the case may be. As shown, for example, in FIGS. 13-15,the outside diameter of the flange, washer and exposed edge of the NPSpipe can be essentially equal, providing means for the shutoff valve tobe easily reconnected onto the exposed pipe end, rendering the BFPinvisible and tamperproof when the line is again pressurized.

Also, with reference to FIG. 1, there is seen orifice 70, ball seat 45and retaining screen 15. Under normal forward flow ball 5 is pushedagainst the inside (proximal side) of retaining screen 15, which isdesigned such that a fluid can flow easily and freely through transitioncone 60, orifice 70, then around and past the smooth outer surface ofseated ball 5 and through annulus 40, which is a space, or set ofportholes, in retaining screen 15 allowing outward flow between theexterior of seated ball 5 and the interior wall of housing 30. Detailsof retaining screen 15 are described in connection with FIG. 3 below.

FIG. 2 depicts a cross-sectional view of the exemplary BFP of FIG. 1subjected to a flow reversal, or backflow condition. In such acircumstance, where the fluid flow reverses direction, ball 5 ishydraulically and instantly forced off the interior of retaining screen15 and seated on annulus 45 (also referred to sometimes herein as “checkvalve seat”), thus occluding orifice 70. It is this functionality whichonly allows fluid flow in the forward direction, and thus preventsbackward flow, thus precluding the introduction of contaminants upstreaminto the water supply lines. When the direction of flow again changesand thus returns to normal (the situation of FIG. 1) fluid dynamics willforce the ball back to reposition itself on the interior of retainingscreen 15.

FIG. 3 depicts an end view (i.e., from the downsteam side, or the farleft of FIGS. 1-2 looking rightward into the BFP from its exterior) ofthe retaining screen of the BFP assembly. Retaining screen 15 keeps ball5 (not shown) operational at all times by providing means for the ballto instantly respond to the fluid dynamics of a given condition, i.e.,normal or reverse flow, regardless of existing differential pressures orrate of flow.

Thus, in exemplary embodiments of the present invention, during normalflow, hydraulic conditions will force ball 5 (also sometimes referred toas a “check ball”) to instantly position itself on the mated concavesurface of the tapered/flat radial spokes 25, and axial hub/seat 65, andstay there, regardless of the physical orientation of the insertablebackflow preventer assembly, i.e., vertical or horizontal, or the flowrate, since the ball has a specific weight close or equal to the fluid.Any fluid can, for example, flow with relative ease around the ball,through the three downstream portholes 55 formed by the three radialspokes 25. The retaining screen with the tapered (streamlined edge)spokes 25, center flushing hole 35 and portholes 55 also provide meansfor an exemplary ball to be instantly displaced and hydraulically forcedoff hub/seat 65 when the flow reverses, regardless of the reverse(backflow) rate of flow. Such functionality allows for immediate seatingof the ball even under very low flow conditions, such as where thebackflow pressure differential is very low, as might be applied in anattempt to defeat a conventional check valve. FIG. 16 is a similar viewto that of FIG. 3 or an exemplary BFP. In the exemplary BFP of FIG. 16,tapered spokes 25 have been tapered on both ends, and their outwardedges shaved for lesser impedance of forward flow.

FIGS. 18 and 19 show an exemplary BFP retaining screen from an upstreamview (i.e., from the right in FIGS. 1 and 2 looking leftward into theBFP). FIG. 18 shows a close up view and FIG. 19 a more distanced view,which shows the portion of the interior of housing 30 in which the ballis contained (i.e., between seat 45 and retaining screen 15, althoughseat 45 is not shown in FIGS. 18-19).

FIGS. 17 and 22-23 depict the exemplary BFP of FIGS. 16-25 with the ballseated on the interior of retaining screen 15, as shown in FIG. 1. FIG.17 shows an inside view, similar to that of FIG. 18, yet here the ballis also shown, and FIG. 23 shows a more distanced view, similar to thatof FIG. 19, albeit with the ball shown. FIG. 22 shows the sameball-retaining screen configuration looking from the outside of the BFPfrom a distal viewpoint, looking through the BFP, a similar viewpoint asis shown in FIG. 16.

FIGS. 20 and 21 are details of the bal seat 45 and orifice 70 of anexemplary BFP, without and with a seated check ball 5, respectively.

FIG. 4 is a graphical illustration showing the operational features andconfiguration of the external and internal components of the insertablebackflow preventer including the housing 30, flange 50, ball 5,transition zone 60, orifice 70, check valve seat 45, tapered edge radialspokes 25, flushing hole 35, port holes 55, ball hub/seat 65 andretaining screen 15 design when subjected to hydraulic conditionscharacterized as normal and reverse flows. Thus, in the top panel ofFIG. 4 a forward flow condition is depicted, and in the bottom panel ofFIG. 4 a backflow condition, where no flow exists to the right of theball seated in the check valve seat 45.

As can be seen from the perspective rendering of the exemplary retainingscreen in FIG. 4 (second drawing from the top on left side of drawing),the tapered spokes can be grooved on their interior side (the side thatthe ball contacts) so as to guide the fluid down them and providing fora thin film of fluid between the seated ball and the hub/seat in aforward flow condition. This allows the ball to rotate randomly whileseated and provides a self-cleaning action thus keeping the ball free ofdeposits or build-up.

FIG. 5 depicts a three dimensional view of an exemplary BFP inserted ina pipe; here normal forward flow is upwards and to the right in thefigure.

FIGS. 6( a)-(c) respectively depict three pairs of force diagrams thatillustrate three different response scenarios of an exemplary BFP whensuch exemplary valve is horizontal, inserted in a pipe 20, and subjectedto very small normal and reverse flows. FIG. 6( a) illustrates whatoccurs when the specific weight of ball 5 is significantly less thanthat of the surrounding fluid, FIG. 6( b) illustrates the scenario whenthe specific weight of the ball is significantly greater than that ofthe surrounding fluid, and FIG. 6( c) illustrates that when the specificweight of the ball equals (or substantially equals) the specific weightof the fluid. In FIG. 6, F1 is a buoyancy force, F2 is the force ofgravity acting on the ball, F3 is fluid pressure, F4 is surface frictionopposing fluid pressure, and F5 is the reactive push downward of housing30 on a ball compressed up against it.

Thus, with reference to FIG. 6, each pair of diagrams show the cagedball with different specific weight relative to the surrounding fluid.Each pair of figures illustrate the fluid dynamics and performancecharacteristics of the caged ball, which is designed to move freely,i.e., laterally and longitudinally, in the surrounding fluid inside thevalve housing and chamber. FIG. 6( a) illustrates the caged ball'sperformance when the flow rate is very low, and, the specific weight ofthe ball is substantially less than the specific weight of the fluidimmersed therein, creating underflow. Said condition can result in avalve's inability to prevent backflow. FIG. 6( b) illustrates a freelysuspended caged ball's performance when the flow rate is very low, andthe specific weight of the ball is substantially greater than thespecific weight of the surrounding fluid, resulting in an overflowcondition when the ball is subjected to normal or in reverse flow.Again, this condition can also compromise a valve's ability to preventbackflow.

The third pair of force diagrams, FIG. 6( c), show the fluid dynamicsand performance characteristics of the caged ball designed in the fluid,each having substantially equal specific weights, eliminating anypossibility of having an underflow or overflow condition and associatedbackflow preventer insert valve failure. The situation of FIG. 6( c) canbe used in exemplary embodiments of the present invention where one BFPis provided, thus insuring operation under the entire gamut of flowrates. It is noted that where system pressure is relatively high, anattempted compromise of the water system via a backflow introduction ofa noxious substance would often operate under a small net backpressure,it being difficult to generate a large backpressure against an alreadylarge forward pressure of, say 70 psi, and still remain undetected.

Gravitational effects are essentially non-existent in the circumstanceof FIG. 6( c), where the ball's specific weight is equal to the specificweight of the surrounding fluid. Therefore, the ball's position withinthe check valve can be governed entirely by the direction and velocityof the flow, the surface area of the suspended ball, friction, fluidviscosity, and thus the force associated with the flowing fluid.

However, it is possible that a contaminant introduced into a fluid, forexample, could theoretically change the specific weight of the fluid,depending on the chemical properties of the contaminant and those of thefluid+contaminant solution. Thus, in exemplary embodiments of thepresent invention, two or more BFPs could be provided in series (as anintegrated device with only one flange at the distal end of the mostdistal BFP stage, or at two closely separated points using twoindividual BFPs), each BFP having a ball with a different specificweight, designed, respectively, to be substantially equal to that of thesurrounding fluid in the presence of various solutes and to that of thefluid itself under normal conditions, thus insuring backflow preventionacross a range of fluid specific weights, even under low differentialbackpressures. Such a multi-stage BFP apparatus could also be used influid systems where different fluids are sent through at differenttimes.

Thus, in exemplary embodiments of the present invention, a BFP canprevent fluid backflow from the valve's fluid outlet to the valve'sfluid inlet when the pressure at the fluid inlet is less than thepressure at the downstream fluid outlet. As long as the fluidpressure—the normal flow condition—is greater at the BFP's fluid inlet(upstream) end relative to that at the valve's fluid outlet (downstream)end, the ball will position itself near the retaining screen's concaveaxial hub 65 (with reference to FIGS. 4 and 17, 22-23). Tests haveconfirmed that ball 5 does not generally make total compressive contactwith the concave surface of the axial hub 65, but, rather, remains insuspension when flow rates exceeded 2-3 gallons per minute.

In such a situation, as shown, for example, in FIG. 6( c) and FIG. 1,the ball can remain in compressive contact with a fluid layer flowingalong the concave surface of hub/seat 65 (and through hole 35) at thecenter of retaining screen 15. Such a layer of fluid can be generated bythe three radial spokes 25 and axial hub/seat 65 that form retainingscreen 15, all having a concave upstream surface, said radial spokes andhub having a flat leading edge that provides means for the three radialspokes to intercept and redirect a fraction of the fluid flowing duringnormal flow towards the central axial hub and the hole therethrough.

FIG. 7 is a plot of head loss across an exemplary BFP as inserted in a ½inch thermoplastic test pipe, subjected to hydraulic pressures between50-60 psi, and, a relatively high rate of flow approaching 3 gallons perminute, using check balls made of different materials with differingspecific weights. Materials tested included polypropylene with aspecific weight of 0.91, polycarbonate at 1.21, Delrin® at 1.42, ceramicat 4.2, and high impact polystyrene 1.03. These observations clearlyshow a minimal impact of a BFP on water pressure.

The caged ball assumes a new position on the concave axial/ball seat 65of retaining screen 15 each time flow ceases and normal flow is resumed,or on the check valve's orifice/seat annulus 45 when the check valve issubjected to a flow reversal. This operational characteristic caninsure, for example, continuous self-cleaning action of the ball sincethe ball 5 automatically positions itself differently on the concaveseat/hub 65 of the retaining screen 15 each time the flow cycles on andoff, exposing a different part of the caged ball's outer surface to thescouring velocity of the flowing fluid.

As noted, in exemplary embodiments of the present invention the backflowpreventer valve performs flawlessly when ball materials have a specificweight substantially equal to the specific weight of the surroundingfluid, even when subjected to very low flow reversals (backflow) flowrates, e.g., less than 1 liter/minute, or differential pressures lessthan 1 psi. The specific weights of exemplary balls tested ranged from a0.93 for Low Density Polyethylene (LDPE) to 1.41 for Delrin®,polycarbonate and High Impact Polystyrene (HIPS) having a specificweight of 1.03. Very low flows were measured volumetrically.

As noted, in the event the pressure at the valve's fluid inlet(upstream) becomes less than the fluid pressure at the valve's fluidoutlet, ball 5 can, for example, automatically unseat from the matedconcave shaped axial seat hub 65 located on the retaining screen 15, andthen be forced by the pressure gradient of the fluid against annulus 45,thus shutting off orifice 70 and preventing any substantial liquidbackflow through the valve.

FIGS. 8-11 depict exemplary installations of an exemplary BFP upstreamof a fixture's shut-off valve. FIG. 8 is a sink installation, FIG. 9 oneon the utility's side of a water meter, FIG. 10 in a wall behind atoilet's supply line, and in FIG. 11 upstream of a generic copper pipecompression fitted shut-off valve.

Recognizing the critical function of a BFP according to the presentinvention to safely and effectively protect potable water systems fromany possibility of accidental or intentional reverse flow contamination,and, to insure safe, essentially flawless and maintenance free operationover a protracted period, selected materials can be identified for anexemplary valve's construction. Such materials can include, for example,304 Stainless Steel, lead-free brass or other advanced weight polymersdeemed safe by appropriate testing organizations (such as, for example,NSF) for the housing. For the ball, for example, hollow 304 stainlesssteel, porous or hollow ceramics, or special advanced light-weightpolymers, such as, for example, Udel® a polysulfone, amorphous highperformance thermoplastic that offers excellent mechanical and chemicalresistance, can be used. In particular, Polysulfone's properties remainrelatively consistent over a broad range of temperatures up to +300° F.(+149° C.), which are important in said application.

Udel® offers hydrolysis resistance for continuous use in hot water andsteam at temperatures up to 300° F. It also provides high chemicalresistance to acidic and salt solutions, and good resistance todetergents, hot water, and steam. Polysulfones have excellent radiationstability and offer low ionic impurity levels. Food-grade Udel®, apolysulfone, is FDA, NSF, 3A-Dairy and USP Class VI compliant. Otherpotentially suitable advanced polymers include, for example,PolyEtherEtherKetone (PEEK), HDPE and Radel® 5000/5001. Radel, a PESPolyethersulfone amorphous high performance thermoplastic is NSF 61certified, possess high heat deflection temperatures properties and hasgood hydrolytic stability.

In exemplary embodiments of the present invention retaining screen 15can be formed by three equidistant radial spokes 25, which can, forexample, join at a central axial hub 65 and have a concave surface onthe (upstream) inward side of the retaining screen. Such exemplary threeradial spokes 15 can also, for example, possess two additional importantdesign features: a flat leading edge, and a tapered trailing edge. Thelatter to insure that freely suspended ball 5 instantly responds to evena very low backflow flow condition. Such a tapered trailing edge canimprove the fluid dynamics of the valve by promoting and redirecting thefreely suspended ball 5 and forcing it into the seat (annulus) 45 of thecheck valve when flow, whether large or very small, reverses direction.Additionally, a flat leading edge (i.e., the part of the spoke whichcontacts the housing being essentially flat, or perpendicular, to theforward flow; a close view of FIGS. 18-19 shows the flat shape of thedepicted spokes where they connect the interior of the housing, and thenthe fact that they are then at an angle less than 90 degrees to the flowdirection as they meet the hub/seat 65) of radial tapered spokes 25revealed a critical interdependent relationship with flushing hole 35and the configuration of hub/concave seat 65, which clearly enhancedball stability over a wide range of fluid flow. The flat leading edgeprovides means for the three tapered radial spokes 25 to intercept andredirect a fraction of the fluid flowing during normal flow, which isperpendicular thereto, towards the central axial hub/seat 65 and throughhole 35.

As noted, bench observations confirmed a very slow rotation of anexemplary ball 5, clearly indicating that the ball was not incompressive contact with the retaining screen 15 itself, rather, ridingon a very thin film of the surrounding fluid, which was very apparentwhen the valve was subjected to normal flow rates greater than 2 gpm,creating a self-cleaning feature that is clearly associated with theunique flat-tapered surface design of tapered radial spokes 25.

In exemplary embodiments, since exemplary retaining screen 15 is concave(internally; as shown in FIG. 2) the caged ball mates with the hub/seat65 of the retaining screen, when the direction of flow is normal.

For reverse flow, seat (annulus) 45 can have, for example, a circularflat surface that is inclined to the longitudinal axis, forming asurface that resembles a truncated cone, or alternately, exemplary ballseat can be, for example, circular and simultaneously have acircumferentially mated seat whose surface is identical to the radius ofthe ball. If there is no flow the suspended ball 5 moves freely withinthe caged area of the valve, neither floating nor sinking, providingthat the ball's specific weight is substantially equal to the weight ofthe surrounding fluid, as noted.

For the ball to have a specific weight substantially equal to that ofthe surrounding fluid, balls made, for example, of materials that have amuch greater specific weight than the intended fluid, such as forexample, water, can be, for example, hollow, or porous internally. Suchan exemplary porous ball must have a non-porous outer surface, such as aceramic coating. In either case, such materials are preferably durableand having a non-porous surface coating that is compatible with thehousing material and structurally sound to insure long term maintenancefree performance.

Properly installed, an exemplary BFP is invisible, chemically resistantand can be performance tested by remote means. Such a ball can, forexample, prevent the possibility of any backflow either accidentally, orby the intentional injection of a toxic liquid contaminant into abuilding's drinking water supply system by using a hose and smallelectrically operated pump that is capable of reversing the hydraulicflow in a drinking water supply system and injecting a toxic liquid orcontaminants (such as, for example, stored in a container, tub or poolin a private residence) into the building and from there into the city'swater supply.

In exemplary embodiments of the present invention, an insertablebackflow preventer can be installed, i.e., inserted, or, for example, byemploying a uniquely designed control/backflow prevention valve or“extension coupling” either having an internal check valve connected asdeemed appropriate, to the discharge (downstream) end of NPS pipe ortubing, as appropriate, that will become exposed when the water shut-offvalve that controls the flow to a water fixture, e.g., bathroom,janitor's closet, etc, is removed exposing the pipe (or tube) end. Insuch embodiments water pressure can be terminated at the upstream sideof the shutoff valve before any attempt is made to remove the shutoffvalve. The water shut-off valve can be temporarily removed exposing theend of the NPS pipe, which is connected to the existing building's watersupply distribution plumbing system. Once the insertable backflowpreventer is installed (inserted into the exposed end of the NPS pipe)the shut-off valve can be, for example, reconnected and madeoperational. A combination control/backflow prevention valve in asimilar vein can replace the existing pipe or “sweated” water supplyshut-off valve that is affixed to a pipe or copper tubing.

As noted a prophylactic water supply system upgrade could be done at theterminus where the water supply control shut-off valves for the variouswater fixtures for a bathroom, kitchen, janitor's closet, drinking waterfountain, etc., are located. Or, alternatively, such installation couldbe done at other locations within a building as may be desired.

The present invention overcomes the limitations of the prior art byproviding means to prevent an accidental or willful internal crossconnection of a building and/or regional municipal potable water supplydistribution system, in manner that is truly cost-effective.

An exemplary BFP can be easily and quickly installed in any plumbingconfiguration, i.e., vertical, horizontal, or inclined. It can operateproperly under a wide range of normal flow rates for a given pipe size,and can perform as intended when subjected to exceptionally low backflowrates and differential pressures. The valve can be self-cleaning, anddue to the specific weight being substantially equal to the fluid's, itsoperation can be unaffected by, and not dependent upon, gravity.

With reference to FIGS. 1-2, washer 10 can be made, for example, of apolymer material, however, such washer is not necessary when the BFP isprovided in a copper tube that has a soldered connection creating a leakproof seal between the valve and copper tube. Flange 50 as well as theBFP's materials can be, for example, engineered to withstand elevatedmaterial stresses due to flow reversal, such as water hammer, that couldbe generated when an attempt is made to introduce a substance into abuilding's water supply distribution system, by means that will exceedthe buildings water supply pressure. As noted, the outer diameter of theflange and washer can be the same size as that of the end of the NPSpipe thread or copper tubing, if the latter is used with a compressionfitting, providing means for the shutoff valve, or union, to be easilyreconnected, once the insertable backflow preventer is properly seatedinside the NPS pipe and the shutoff valve or union is reconnected.

In exemplary embodiments of the present invention re-plumbing is notnecessary to install a BFP as existing piping lengths are maintained.Additionally, other locations in a facility's water supply pipingdistribution system besides upstream of shut-off valves leading tofixtures can, for example, be selected, such as, for example, a pipejunction, where two pipes are connected by a pipe coupling or extensionadapter.

Once installed, in exemplary embodiments of the present invention aninsertable backflow preventer, or a combination control/backflowprevention valve, the latter consisting of an integrated shutoff valveand a BFP according to an embodiment of the present invention, candramatically improve the internal security of a potable water supplydistribution system in a building; preventing means by which one could,with relative ease, successfully introduce or inject a contaminant usinga hose and electrically operated liquid pump, or other such means intothe buildings water supply system via a fixture. It is noted that a pumpwith an operating discharge pressure rating that is greater than abuilding's water pressure can easily inject a toxic fluid into thebuilding's plumbing system, and once online completely unattended. Suchan injection process could involve (i) connecting a discharge hose thatis connected to the discharge end of the electrical pump to a waterfixture (spout) or shutoff valve; (ii) with the supply (suction) hoseconnected to the pump's suction end, placing the other end of the hoseinto a nearby container, tub or even a residential pool, holding toxiccontaminants; and (iii) opening the fixture's water supply faucet(valve) and turning on the pump. The toxic fluid held in the container,tub or pool can be thus completely emptied, being automatically injectedby the pump's action into a water supply system and possibly a municipalpotable water supply system, without any need for further personalattention.

According to another exemplary form of the invention a single unitarythin wall cylindrical valve body can have, for example, an elongatedbarrel with a recessed retaining screen—the recessed design eliminatingany solder from dripping onto the radial spokes and axial hub (with holetherethrough) at the flanged end when the apparatus is used withcopper/soldered tubing to insure complete insertion into the tubing,rendering it invisible to the naked eye and tamperproof. A washer is notrequired when the apparatus is inserted in a copper tube with solderedconnections.

A unique aspect of the invention is the use of a freely suspended objectthat is immersed in a fluid with the same, or nearly same, specificweight. Such design provides simple yet effective means whereby thefluid can instantly control the desired functional position of theobject. Such an object can be a sphere, as illustrated above, or, forexample, can take any shape or form, e.g., a cone or cylinder, dependingon the specific application.

According to another exemplary form of the invention, an exemplary BFPcan form an integral part a conventional water meter, where such BFP islocated on the upstream (normal flow) side of the water meter tominimize head loss during periods of normal flow.

Thus, a BFP according to an exemplary embodiment of the presentinvention can provide a self cleaning, super-low head loss andcost-effective valve that can protect an individual building's watersupply system or that of a municipal waterworks from being compromisedby either an accidental or intentional cross connection. Such a BFPobviates any need to completely replace the pipes in a building ormunicipal piping system when there was exposure to a hazardouspersistent contaminant, an agent that simply cannot be flushed out ofthe building's or the municipality's potable water supply pipedistribution system.

Such an exemplary BFP:

1. With relative ease can be quickly installed, i.e., inserted intoexisting or new pipe or copper tubing in the shortest time possible, andunlike conventional backflow preventers is not visible to the naked eye,is chemically resistant and essentially tamperproof;2. Is mechanically simple with only one moving part, a ball, that isself-cleaning, insuring extended maintenance and trouble free operation;3. Is housed in a valve body that has a flow transition zone to minimizehydraulic head loss when the check valve is operating in the normallyopen position;4. Has an orifice with a recessed edge design that will enhance sealingcharacteristics when flow reverses and the ball is forced onto the seat,said ball having the characteristics of moving freely off the (closedposition) seat when fluid flow returns to the proper (normal) direction.6. Provides means to easily ascertain if said backflow prevention valveinsert is working properly, without having to expose or remove it fromwithin the facilities water supply distribution pipe or system. Such atest can be performed by connecting a fluid injecting apparatus to theappropriate shutoff valves fixture spout, then opening the fixturevalve, activating the pump and observing system pressure and fluid flow;7. Is easier to manufacture, install and service than conventionalbackflow preventers, which are inherently massive, mechanically complexand because of their mechanical complexity prone to malfunctions.Fire Hydrant Security

In exemplary embodiments of the present invention, fire hydrant securitycan be enhanced using one or more BFP(s), albeit with a shorter inlettransition to minimize space requirements in certain applications.

Existing hydrants, such as are shown in FIGS. 26-30 and 32, can bemodified to prevent the possibility of accidental or the intentionalintroduction (backflow) of a toxic agent, by simply retrofitting themwith two series BFPs. The check valve(s) can, for example, be housed asfollows: the first (upstream, normal flow) valve can, for example, beinstalled, in the horizontal, exposed outlet of the hydrant, the gasketand flange of the backflow valve in compressive contact with the exposedend of the hydrants outlet. The check valve can contain a ball with aspecific weight that is close to, or equal, to the specific weight ofwater. The threaded female end of an assembly consisting of a 45 degreeelongated elbow can then be connected to the hydrant's male threadedoutlet and permanently fixed, for example, tack welded, to the hydrant'soutlet in a manner that said elbow makes a 45 degree angle with thehorizontal. The exemplary assembly can have a second backflow checkvalve (downstream of the first valve), that when installed, for example,tack welded to the hydrants threaded outlet, is not visible even bypeering inside the housing pipe opening with the naked eye.

The specific weight of the ball in the second (downstream) backflowvalve can, because of the physical orientation of its orifice and seat,have the lowest specific weight technically possible, effectivelypreventing the reverse of any fluid or pressurized gas that exceedssystem water pressure, or otherwise having a sufficient force to seatthe check ball into the valves orifice. Valves positioned in this mannercan, for example, use housing and ball materials approved by the NSF,such as, for example, 304 L stainless steel. It is noted that the ballsmust be hollow if 304L stainless steel or titanium is selected to meetthe specific weight criteria described above.

As shown in FIGS. 32-35 new hydrants can, for example, be equipped witheither one BFP, or, for example, two or more in series. Such an assemblycan prohibit the injection of fluids having physical properties thathave extremely low or high specific weights, such as, for example,naptha, a liquid when slightly chilled having a specific weight of 0.67,carbon tetrachloride a liquid having a specific weight of 1.59, orlethal gases such as, for example, chlorine, phosgene, etc.

Given the possible introduction of toxic liquids and/or gases withvarying specific weights it is imperative that such an exemplary seriesconfiguration be employed to effectively address extremes in specificweight and other chemical factors. The valve's simple design replicates,and can even exceed, conventional dual check valve performanceexpectations established by appropriate regulatory entities. As shown inFIG. 33 the exemplary check valve(s) can be installed in a verticalorientation inside the lower section of a hydrant's barrel, immediatelybelow the hydrants valve seat, with retaining screen always orientedupwardly. Valve housing and check valve balls materials selected wouldonly be those approved by appropriate certifying entities, e.g., theNSF. The balls would be hollow if 304L stainless steel, or some othermetal alloy like titanium is employed, or solid ceramics orthermoplastics with specific weights that are substantially more thanthe fluid (water), equal to fluid, or heavier than the fluid (liquid)based the valves' orientation in the hydrant or lateral water supplyline. Other ball specific weight and material properties, criticalselection factors, must be considered when addressing the introductionof lethal gases and/or toxic liquids, when more than one check valve isemployed.

FIGS. 34 and 35 depict one or more BFPs located inside a hydrant's watersupply pipe in a lateral position that is between the hydrant's streetshutoff valve and the hydrant, i.e., inside the water supply pipelateral that is upstream of, and connected to, the hydrant, and,downstream of the shutoff that controls the flow into the hydrant. Checkvalves placed in the lateral pipe drinking water supply pipe, which isessentially horizontal, would use balls with specific weights that areclose or equal to the specific weight of water.

Modifications and alternative embodiments of the invention will beapparent to those skilled in the art in view of the foregoingdescription. This description is to be construed as illustrative only,and is for the purpose of teaching those skilled in the art the bestmode of carrying out the invention. The details of the structure andmethod may be varied substantially without departing from the spirit ofthe invention and the exclusive use of all modifications, which comewithin the scope of the appended claims is reserved.

What is claimed is:
 1. A valve, comprising: a valve body; a retainingscreen at a distal end of said valve body, said retaining screencomprising at least two radial spokes each connected between a peripheryof said screen and a central hollow ring, said radial spokes beingcurved longitudinally so as to distally offset the central ring fromsaid distal end of said valve body, and said spokes arranged to redirecta portion of a fluid during forward flow towards said central ring; aball seat at a proximal end of said valve body; and a ball; wherein theball is caged between the retaining screen and the ball seat, whereinthe radial spokes are each tapered transversely so as to form a canal toguide the fluid, and wherein in forward flow the ball is held in an openposition by the retaining screen such that forward fluid flow isfacilitated, said ball being suspended on a layer of fluid flowingbetween a surface of the ball and an inner surface of said retainingscreen, and in backwards flow the ball seals in the ball seat in aclosed position, thus preventing backflow.
 2. The valve of claim 1,wherein the valve body has a flange provided on its outside at one end.3. The valve of claim 2, wherein the flange has an outside diameter thatallows the valve to be inserted into an inlet side of a shutoff valve orconnection fitting.
 4. The valve of claim 2, further comprising a flangewasher in compressive contact with the flange and an exposed edge of apipe and/or tube when the valve assembly is inserted into said pipe ortube.
 5. The valve of claim 1, wherein the valve body has an outsidediameter that provides for the unobstructed insertion of the valve intoa pipe or tubing such that once installed the valve is not visible. 6.The valve of claim 1, wherein the ball seat defines an annular surfacein a plane normal to the flow path, and wherein the seat is operable toclosably seat the ball during backflow.
 7. The valve of claim 1, whereinin operation the ball is immersed in the fluid, and wherein said fluidand the ball have substantially equal specific weights.
 8. The valve ofclaim 1, wherein the retaining screen has equidistant radial spokes,each pair of spokes being respectively separated by port holes, andwherein in forward flow the fluid flows through said port holes.
 9. Thevalve of claim 1, wherein the central ring surrounds the axial center ofboth the retaining screen and the valve body.
 10. The valve of claim 1,wherein the valve body is cylindrical.
 11. The valve of claim 1, whereinthe valve body has a flow transition zone to minimize hydraulichead-loss when the valve is in the normally open position.
 12. The valveof claim 1, wherein the ball seat incorporates a recessed mating edgesurface to enhance sealing characteristics when the valve is in a closedposition.
 13. The valve of claim 1, wherein the ball rotatessubstantially in place on said layer of fluid flowing between a surfaceof the ball and an inner surface of said retaining screen.
 14. Anintegrated control/backflow prevention valve assembly, comprising: avalve according to claim 1; and a control shutoff valve.
 15. Anextension adapter, comprising: at least one valve of claim 1, whereinsaid extension adapter is capable of being affixed to a fluid supplyline.
 16. A water supply meter comprising at least one valve accordingto claim 1, said meter capable of being affixed to a fluid supply line.17. A fire hydrant that includes at least one valve according to claim1, said fire hydrant capable of being affixed to a fluid supply line.18. The backflow preventer valve of claim 1, wherein the ball has aspecific weight that is a defined function of the specific weight of afluid to be sent through the valve.
 19. The backflow preventer valve ofclaim 18, wherein the ball has a specific weight approximately equal toa specific weight of a fluid to be sent through the valve.
 20. Thebackflow preventer valve of claim 1, wherein in forward flow the ball isat least one of self-cleaning and exhibiting low head-loss.
 21. Abackflow preventer valve, comprising: a valve body; a retaining screenat a distal end of said valve body, said retaining screen comprising atleast three radial spokes, each spoke connected between a periphery ofsaid screen and a central hollow ring, said radial spokes being curvedlongitudinally so as to distally offset the central ring from saiddistal end of said valve body, said spokes arranged to redirect aportion of a fluid during forward flow towards said central ring andsaid spokes each being tapered transversely so as to form a canal toguide the fluid towards said central ring; a ball seat at a proximal endof said valve body; and a ball; wherein the ball is caged between theretaining screen and the ball seat, and wherein in forward flow the ballis held in an open position by the retaining screen such that forwardfluid flow is facilitated, said ball being suspended on a layer of fluidflowing between a surface of the ball and an inner surface of saidretaining screen, and in backwards flow the ball seals in the ball seatin a closed position, thus preventing backflow.
 22. The backflowpreventer valve of claim 21, wherein the ball has a specific weight thatis a defined function of the specific weight of a fluid to be sentthrough the valve.
 23. The backflow preventer valve of claim 22, whereinthe ball has a specific weight approximately equal to a specific weightof a fluid to be sent through the valve.
 24. The backflow preventervalve of claim 21, wherein in forward flow the ball is at least one ofself-cleaning and exhibiting low head-loss.